Guarantee???

I know this should be in the landscape forum, but I kind of need an answer fast. I just want to know from those of you who install plants, what is your mark-up % for your guarantee.

Example: 1 Colorado Blue Spruce. Your Cost $99.00
What is the amount you would mark up the tree for your guarantee. PLEASE NOTE: I'm not looking for a price for the labor involved or the mark-up for the extra jingle in your pocket as well, JUST THE GUARANTEE! Thanks all!

JD: I never guarantee any plant materials other than to be true to name. I have however guranteed large field dug b&b trees. Just double your price for the tree. Figure half of total cost for install and if the sucker dies then your out the labor to replace it. You need to put a disclamer in your paperwork stating you cannot be responsible for plants, trees, and etc, after they leave your care. The only reason I guarantee large trees is because if someone is spending thousands of dollars on a tree or trees they are most likely going to care for their investment.